All angle base detonating fuze

ABSTRACT

A BASE DETONATING FUZE FOR USE WITH A HIGH EXPLOSIVE SHELL INCLUDING AN INERTIA WEIGHT STRIKER HAVING UNIQUE SPHERICAL SURFACES IN LOOSE CONTACT WITH THE BORE OF THE BASE PLUS SUCH THAT THE MASS CENTROID OF THE STRIKER IS NOTICEABLY FORWARD OF ITS CONTACT AREA. OBLIQUE ANGULAR CONTACT OF THE SHELL WITH THE TARGET PRODUCES AN INTERTIAL TORQUE COUPLE AND CAUSES A FORWARD &#34;ROLL&#34; OF THE STRIKER THEREBY CONTACTING THE FIRING PIN IN EXACT CENTER AND APPLYING THE REQUIRED AXIAL THRUST THERETO.

Nov. 2, 1971 n. M. DAVIS 3,616,755

ALL ANGLE BASE DETONATING FUZE Filed June 11, 1969 I J h I ll INVENTOR. D4441 Jk. Z714 W8 Joy-rage rs 3,616,755 ALI. ANGLE BASE DETONA'IIING FUZE Dale M. Davis, Freeport, Fla, assignor to the United States of America as represented by the Secretary of the Air Force lFiled June 11, 1969, Ser. No. 832,112 lint. Cl. F42c 15/22 11.5. Cl. 102-73 A 4 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates to a base detonating fuze for a high explosive shell and, more particularly, the invention is concerned with providing a fuze positioned in the base of a shell and having a novel striker design which functions reliably regardless of the angle of obliquity of contact of the shell with the target.

Base detonating fuzes normally operate from the inertia of the firing pin, sometimes being spring assisted. This arrangement is quite satisfactory and suificiently sensitive to operate in direct head-on impact. However, where the angle of impact of the shell with the target is slightly oblique, the presently available base detonating fuzes are unreliable and insensitive and generally result in a high percentage of duds. The reason for this lack of functional reliability is that the forces acting on the firing pin at impact are obliquely oriented and, therefore, because of the configuration and confinement of the firing pin arrangement, high frictional resistance acts on the firing pin to absorb a significant portion of the impact force thereby preventing the required rapid axial movement toward and into the detonator.

In order to provide a base detonating fuze which is sensitive and highly reliable at all impact angles, it is necessary for the firing pin to reach and penetrate the detonator with sufficient force to initiate the explosive chain. This generally would require that a force of relatively large magnitude and substantially axial, that is, along the central axis of the shell, be applied to the firing pin on impact of the shell with the target. The hereinafter described invention fulfills the above mentioned requirements and eliminates the shortcomings of presently available base detonating fuzes.

SUMMARY OF THE INVENTION The present invention provides a base detonating fuze which includes a novel striker having spherical surfaces in loose contact with the bore of the base plug. The striker acts as an inertia weight and when the shell strikes the target, the deceleration causes a forward movement of the striker which contacts the firing pin and drives it into the detonator. The unusual configuration of the striker places its mass centroid forward of its contact point with the bore of the base plug so that contact with the target at any angle (other than point on) will result in an inertial torque couple which will roll the spherical striker down the bore, the leading point contacting the firing pin in exact center and applying an axial thrust thereto. Thus, the fuze will be sensitive and function reliably regardless "nited States Patent of the angle of obliquity of the target and the high percentage of duds common to other presently known base detonating fuzes will be eliminated.

Accordingly, it is an object of the invention to provide a base detonating fuze which is capable of functioning reliably regardless of the angle of obliquity with the target.

Another object of the invention is to provide a base detonating fuze for use in an armor piercing high explosive shell having a blunt nose. The fuze includes a spherical striker which rolls into the firing pin after contact of the shell with the target.

Still another object of the invention is to provide a base detonating fuze wherein an inertia weight which operates as a striker includes spherical surfaces in loose contact with the bore of the base plug and the base of the firing pin.

A further object of the invention is to provide a base detonating fuze wherein the striker operating as an inertia weight is constructed and arranged to strike the firing pin on exact center regardless of the angle at which the projectile strikes the target.

A still further object of the invention is to provide a base detonating fuze wherein the mass centroid of a striker having spherical surfaces is forward of its contact area with the bore of the base plug so that contact with thet target at an oblique angle will result in an inertial torque couple which will roll" the spherically surfaced striker along the bore with substantially friction-free movements upon target impact.

These and other objects, features, and advantages will become more apparent after considering the description that follows taken in conjunction with the attached drawings and appended claims.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a typical armor piercing high explosive shell showing the positioning of the base detonating fuze therein; and

FIG. 2 is a cross-sectional view of a base detonating fuze according to the invention suitable for use in the shell of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, the all angle base detonating fuze 13 according to the invention includes a base plug 15 threadably attached to the base of a high explosive armor piercing shell 17 (shown in FIG. 1). The shell 17 is provided with a steel cap 19 on the forward tip of the body portion 21. On the outer wall of the body 21 there is attached a rotating band 23 and the inner cavity of the shell 17 is filled with an explosive material 25. The base detonating fuze 13 is in direct contact with the rearward surface of the explosive charge 25.

The base detonating fuze 13 is provided with an inertia weight striker 27 positioned in contact with the inner surface of the base plug 15. The striker 27 is a portion of a sphere and the spherical surfaces are in loose contact with the bore 29* of the base plug 15 and with the base of a firing pin 31. A firing pin spring 33 holds the firing pin 31 and the striker 27 rearward when the shell 17 exits the muzzle after tiring in order to overcome the effect of aerodynamic deceleration. The firing pin 31 and firing pin spring 33, are positioned in the aft body 35.

In the rearward section of the forebody 37, there is positioned a ball rotor 39 with a detonator 41 occupy ing the central portion thereof. The detonator '41 is in an out-of-line or safe position and the ball rotor 39 is held forward by the ball retainer 43 which is located between the aft body 35 and the forebody 37. In the forwardmost section of the forebody 37, there is positioned a booster 45 between the ball rotor 49 and the explosive charge 25 (FIG. 1).

The hereindescribed base detonating fuze 13 functions with complete reliability regardless of the angle of obliquity of the target. This is a result of the novel configuration of the inertia weight striker 27 which allows a rolling motion down the bore 29 to contact the firing pin 31 exactly on center and, except for the small friction between the striker 27 and the firing pin 31, all of the axial thrust is applied directly to the firing pin 31.

MODE OF OPERATION The fuze assembly 13 as shown in FIG. 2 is in the safe position prior to firing. Upon firing through a rifled gun tube, setback or acceleration produces forces which urge the ball rotor 39 containing the out-of-line detonator 41 rearward against the ball retainer 43 and the aft body 35 when friction forces cause the rotor 39 and retainer 43 to spin at the same rate as the fuze 13 and projectile 17. In like fashion the inertia weight 27 and firing pin 31 are also caused to spin along with the other parts.

After exit from the muzzle, setback forces no longer apply and the retainer 43, rotor 39, striker 27, and firing pin 3-1 are free to move within their physical constraints. The well known arming of the fuze 13 now occurs by the retainer ring 43 expanding outward by centrifugal force releasing the rotor 39 permitting it to seek its position of maximum moment of inertia, that is, aligning the detonator 41 along the central axis of the projectile 17.

One of the new and novel features of the hereinbefore described base detonating fuze resides in the inertia weight striker 27 and its unusually high sensitivity to glancing blows which occur in the common case of oblique contact with the target. During firing, the striker 27 and firing pin 31 are held rearward by bore acceleration. Upon muzzle exit they are held rearward by the firing pin spring 33 which is of sufficient strength only to overcome the effect of aerodynamic deceleration. Alternate designs could employ a shear disc or other well known detent mechanisms.

Upon target impact, the deceleration of the projectile body 21 causes the inertia weight striker 27 to go forward relative to the remainder of the projectile 17 and fuze assembly 13, striking the firing pin 31 and driving it into the detonator 41 which is in axial alignment therewith. Thus, the inertia weight striker 27, because of its configuration and confinement, strikes the firing pin 31 on exact center regardless of the angle at which the projectile 17 strikes the target.

The inertia Weight striker 27 is a portion of a sphere having spherical surfaces in loose contact with the bore 29 of the base plug and the base of the firing pin 31. The mass centroid of the striker 27 is noticeably forward of its contact with the bore 29 of the base plug 15 so that, contact with the target at any angle other than point on, will result in an inertial torque couple which will roll the sphere down the tube. Since the striker 27 reacts like a sphere, the leading point will always contact the firing pin 31 in exact center and, except for the small friction between the striker 27 and the firing pin 31, will apply direct axial thrust to the firing pin 31.

Although the invention has been illustrated in the accompanying drawings and described in the foregoing specification in terms of a preferred embodiment thereof, the invention is not limited to this embodiment or to the particular configurations mentioned. It will be apparent to those skilled in the art that my invention can be used with any other of many well known safe and arming devices. Also, it should be understood that various changes, alterations, modifications, and substitutions, particularly with respect to the construction details, can be made in the arrangement of the several elements without departing from the true spirit and scope of the appended claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent of the United States is:

1. In a high explosive shell, a base detonating fuze comprising a base plug having a forwardly extending bore portion, a frusto-conical inertia weight striker having spherical surfaces at the base portion in loose contact with the bore portions of said base plug, said inertia Weight striker being positioned in the rearwardmost section of the bore portion and being configurated such that its mass centroid is located near its forward end, a firing pin positioned immediately forward of said striker, the leading face of said striker being spherical and in contact with the exact center of the base of said firing pin, a ball rotor located forward of said firing pin, a detonator in the central portion of said ball rotor, means for preventing rotary movement of said ball rotor until said shell exits the muzzle of a gun after being fired, said ball rotor being free to rotate after leaving the muzzle of the gun to allow axial alignment of the detonator with the firing pin so that impact of the shell with the target causes said striker to move forward in a rolling motion and strike the center of the firing pin with sufficient force to drive the firing pin into the detonator causing said shell to explode.

2. The base detonating fuze defined in claim 1 wherein a firing pin spring surrounds said firing pin, said firing pin spring being of sufficient strength to urge said firing pin rearward to overcome the effect of aerodynamic deceleration forces occurring upon muzzle exit of the shell from the gun.

3. The base detonating fuze defined in claim 1 wherein a retainer ring is positioned behind and in contact with said ball rotor, said retainer ring preventing rotation of said ball rotor during travel of the shell through the gun and releasing said ball rotor for rotational movement after exit of the shell from the muzzle of the gun.

4. The base detonating fuze defined in claim 1 wherein a booster is positioned forward of said detonator, said booster being initiated by the firing of said detonator for aiding in the establishment of the explosive train of the shell.

References Cited UNITED STATES PATENTS 1,318,098 10/1919 Midgley 102-73 A 1,321,455 11/1919 Kennedy 102-73 2,417,437 3/1947 Nicholas. 102-73 X 3,371,608 3/1968 Webb 102-73 X 3,397,640 8/1968 Ziemba et al. 102-79 X SAMUEL W. ENGLE, Primary Examiner U.S. Cl. X.R. 102-79 

